A fundamental problem in neurobiology is understanding how the potential for complex behaviors are established. Drosophila melanogaster is an excellent model system to explore this question, given that a robust behavior, mating behavior, is genetically programmed. Drosophila male courtship consists of a series of steps directed towards a female. Females that have not been mated are receptive to male courtship behaviors, whereas those that have been recently mated will reject these advances. There is molecular-genetic evidence demonstrating that the doublesex (dsx) transcription factor plays a role in establishing courtship and mating behaviors in both males and females. However, in both males and females the specific function of dsx in the CNS has not been ascertained. This gap in our knowledge is limiting our ability to fully understand reproductive behaviors at a molecular-genetic level. The long-term goal of the research in my lab is understanding the genetic specification of sex-specific behaviors, using Drosophila as a model system. This will provide a foundation for understanding the specification of complex behaviors in other organisms, including humans, for which we have very limited understanding. The overall objective of the research proposed here is to determine if dsx plays an essential role in the CNS for mating behaviors. Our specific hypothesis is that dsx is required in the CNS in subsets of cells to specify some aspects of male courtship behavior, and to specify all or nearly all aspects of female mating behaviors. [unreadable] [unreadable] [unreadable]